Silica has long been used as a reinforcing filler in tread compounds. Silica is used instead of carbon black and together with special chemical substances (silanes) which interact with the silanol groups of silica to prevent its particles from forming hydrogen bonds. With the right functionality, silanes may also interact with the polymer base to form a chemical bridge between it and the silica. Silica is employed for the advantages it affords in terms of rolling resistance and wet-road-holding performance.
To balance certain physical and mechanical compound properties, it is common practice within the industry to employ a polymer base comprising a mixture of polymers with different physical characteristics. Often, these differences are manifested in the form of different glass transition temperatures.
Using a mixture of polymers with different physical characteristics, however, can pose problems in terms of abrasion resistance. That is, the difference in rigidity of the polymers may result in local stress in the resulting polymer base, which has a negative effect on abrasion resistance.
A need is therefore felt for a method of producing compounds, in which the polymer base comprises a mixture of polymers with different glass transition temperatures, but without impairing the abrasion resistance characteristics of the compound.
The Applicant has surprisingly discovered a method of producing compounds, in which the polymer base comprises a mixture of polymers with different glass transition temperatures, with no problems in terms of abrasion resistance, and which surprisingly also affords advantages in terms of rolling resistance.
With respect to the known art, the method according to the present invention involves no increase in the amount of ingredients, and no additional ingredients in the compounds, but simply alters the timing with which they are mixed. In fact, as anyone skilled in the art knows, using too much or too many types of ingredients makes it difficult to control the various target properties of the compound.